Extract TypeArgumentsVerifier.

I did not do any cleaning up of the extract code.

R=brianwilkerson@google.com

Change-Id: Idbec6e6105f5ec2a32385296c4cfc437b63a17a9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112800
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

Author: scheglov